Alloy metal for bearings



Patented May 12, 1931 UNITED STATES WAL'IHER MATHISIUS MARTIN W.

NEUFELD, or nnnnm-cnmor'rnunune,

- GERMANY ALLOY miru. ron BEARINGS 17o Drawing. Application filedFebruary 24, 1927,

affected in other directions. By the employment of high percentages,such as about 1 per cent., of the different alloy'constituents, eitherthe fluidity of the alloy or its resistance to oxidation isdisadvantageously affected or its brittleness is increased to an extentwhich prevents its practical use as a bearing metal. It has not beenfound possible to raise the hardness of the metal as commercially usedabove 30 or at the most above 35 Brinell (ball pressure) units.

Applicants have discovered that by the addition of a number of differentalloying constituents of the alkali metals and the metals of thealkaline earths, each of which is added in only small quantities, theball pressure hardness can be extended up to 38-41 Brinell units. Thealloy constituents may be used in the following proportions:

0.5% Ca 0.1% Mg 0.5% Na 0.04% A1 0.1% Ba Rest lead This specific exampleconstitutes the sub ject matter of our German Patent 441,071, issuedFeb. 21, 1927. I

Each of these constituents in thepercentage stated is of some influenceon the Brinell hardness of the alloy, so that if the amount of one oranother of these constituents is con- 4 siderably reduced, or if one ofthem is omitted, the Brinell hardness is reduced by 4 or 5 units. Thisalloy has a stationary point in the cooling curve which is stronglymarked at 320 C. On heating to 450 C. it is very fluid and easil poured,and is not injured by heating up to 00 or 800 C. It is not brittle andis especially suited for use as a bearing metal- We have now, sincemaking the invention -set forth in the German patent, discovered of thealloy at high temperatures.

Serial No. 170,735, and in Germany Kay 17, 19%.

that-the hardening eflect is further increased if the content of thealloy metal of the Na group is increased to between 0.6 and 0.65%.

If the Na content is raised above this upper limit, the specifichardening action of this element is essentially decreased, and thefurther increase of the Na content has also the drawback of producing atendency of the alloy to corrode.

The increase of the Na content from 0.5 0.65% has, however, a very largeeffect on the hardening action, so that the alloy constituent barium maybe omitted without reducing the'range of hardening given in theabove-mentioned alloy.

Experience has also shown that definite rules must be observed asregards the ratios of the alloy constituents MgCa and Mg Al, in order toobtain a good result. vThese {ulesare found by experience to be asfolows:

The Mg contentshould be about 4th to 5th of the calcium content and theAl content about half that the Mg content. I

In alloys made according to these rules, it is ,75 found that an 'Alcontent, which, if possible, should not be below 0.05%, exerts anextreme protection" against the tendency to oxidition t is practicallyproved that an alloy having a con- 30 stitution in accordance with theabove-mentioned rules, with a content of 0.05% Al. can be maintained inthe liquid condition for about 15 minutes at a temperature of- 800 C.without any practical waste by burning of 5 the hardening constituents.The maintenance of the alloy under these extreme conditions is probablydue to a complete thin (sintered) covering of slag formed on the uppersurface of the liquid metal which prevents the further entrance ofoxygen or oxidizing air. Only after a long exposure to the oxidizing airat high temperature so that the waste by burning has reduced the Alcontent below 0.035% a rapidly increasing oxidation occurs by which allthe hardening alloy Constituents are more or less burnt out of themetal.

The higher the Al content is raised, within practical limits, thegreater is this protecting action of the Al, so that it is possible, 100

for example, to expose the unprotected surface of an alloy containingabout .0.1%

of Al to the oxidizing action of atmospheric air at 800 C. for an hourwithout any diminution of the ball pressure hardness of the cast alloy.

WVith the above-mentioned rules respecting the numerical relations to bemaintained between the alloy constituents AlMg and Mg-Ca it has beenproved that lead-magnesium alloys with higher content in Mg have highhardening characteristics for a short time after melting and pouring,but that the alloys, in consequence of crystallization, tend todeteriorate and for that reason even with contents of Mg in which thereis no substantial deterioration of the alloy, a decrease of the ballpressure hardness is observed in the course 0 time.

Practical experience has, on the other hand, shown that by maintainingthe above-mentionednumerical relations between the three alloyconstituents AlMg andCa, no reduction of the. ball pressure hardnessoccurs during a very long time.

This result may be explained by the fact that during the addition of Alto a magnesium-lead alloy, in consequence of the small afiinity of Al tolead, also on account of the relatively small content of Al and M thereis a combination between Mg and l corresponding to the type Mg Al whichis soluble in an excess oflead and has a hardening efiect on the latter.

imilarly, with the presence at the same time of Mg and Ca, a ternarycombination between MgCa-.-lead is formed which is also soluble in anexcess of lead, has a hardening action, and does-not show the tendencyto qefteriorate produced by a Mg content by itse From these experimentaresults and also from the rules founded upon them, it is found that theAl content of an alloy of thiskind should not be below 0.1% andcorrespondingly then the Mg content should not exceed 0.2%, whichcorresponds to a mini- .mum Ca content of 0.70.8%.

The manufacture of an alloy with 0.1% of Al presents considerabledifliculties.

It has been known for a long time that lead with considerable excess ofAl melted with it and strongly agitated is capable of dissolving up to0.07% of Al. Such a content of Al can only be obtained if uneconomicallylarge excesses of A1 are melted with the lead. In an economical alloyprocess, relatively high contents of Al shouligl be possible without theuse of an excess of In carrying outthe alloying process in this knownmanner, the content does not essentially exceed 0.04%. j

It is possible by long continued melting at high temperature to raisethis alloy content above the limits of about 0.08% if the Al is added inthe form of a previous mixture of Al-Mg or Al-Ca. But this method ofcarrylng out the alloy process does not afford an economicallysatisfactory result. If, on the other hand, in carrying out the alloyprocess, that is by immersing the Al in a large lead bath, it ispossible within the same apparatus to introduce metallic Mg or metallico9. into the lead with the alloying Al, and in this way the lead takesup the Al in a very surprising and satisfactory manner. In this way in afew minutes by the use of moderate alloy temperatures, for example 500(3., an Al content of 0.2% and more can be easily obtained. This verysurprising result may be due to the fact that the heating of the metalat the moment of immersion produces a strong exothermic chemicalcombination Al-Mg or Al -Ga by which the temperature of the lead alloyis so greatly increased locally that the Al is easily and quicklyabsorbed in the lead bat-h.

From the above-mentioned considerations it is found advisable to changethe alloy contents to the following: 7

(Mill-0.65% Na 0.75l.-% Ca 0.20-0.25% Mg Such an alloy has thepreviously mentioned important properties with respect to covering ofwood charcoal or the like. .The

alloys can be exposed for a longer time at the casting temperature tothe air without oxidation. It may also be recast as often as may berequired without altering its properties,'an'd it is also insensitive tooverheating. In consequence ofthe absence of oxidation, the percentagecontent in the alkali metals and metals of the alkaline earths canbemore exactly proportioned in the manufacture than formerly, sincethere is no considerable waste by burmng to be taken into account. Thisfact economizes the use of the hardening metals and ensures a muchgreater reliability in the compositionof the alloy.

The waste formed in the manufacture and use, in casting and also in thefactory operations, can always be used again, if necessary v no afterthe adjustment to the right composi- 1 tion.

In the above-mentioned alloys a casting small quantities of bismuth,copper or tin, or two or more of these metals so that the castintemperature can be reduced to about 500 This effect occurs withanaddition of Bi of about 0.1% Cu of about 0.1% Sn of about 0.1%

If more than one of these metals is used, the total content should notexceed 0.1%. We claim q 1. A bearing metal consisting of lead hardenedby alkali metals andmetals of the alkaline earths, containing 0.60-0.65per cent. Na; 0.75-1. per cent. Ca; 0.20-0.25 per cent. Mg; 0.10 percent. Al, the Pb constituting the main bulk of the alloy.

2. A lead alloy containing about 0.6% to 0.65% sodium, about 0.7% to1.0% calcium, magnesium equal to about one-fourth to onefifth of thecalcium content, aluminum equal to about half the magnesium content,lead constituting the main bulk of the alloy.

3. A lead allo containing about 0.6% to 0.65% sodium, about 0.7% to 1.0%calcium magnesium equal to about one-fourth to onefifth of the calciumcontent, aluminum equal to about half the magnesium content, about 0.1%of at least one of the metals bismuth, copper and tin, and leadconstituting the main bulk of the alloy.

In testimony whereof we have signed our names to this specification.

PROF. ALTHER MATHESIUS. DR.-'ING. MARTIN W. NEUFELD.

